Great quantities of paints, lacquers, varnishes and clear coat finishes are used in the automobile, appliance, and allied industries to coat finished products. It is well-known that in these industrial paint operations where paint is either applied by a spray-gun apparatus or a Behr Bells system, a portion of the paint is not transferred onto the item being painted. Instead, the paint is left in the air that is present in the paint booth. Currently, industrial paint booths have a series of filtering media to trap the air-borne paint particles before the air from within the paint booth is transferred to the outside environment. The first stage of this filtering process involves the passing of the paint-saturated air through a "curtain" or flood sheet of water. The physical barrier of the water traps the larger paint particles. Since most paint resin systems are hydrophobic, the paint does not become solvated by the water, but will sit on the surface until it comes in contact with a side wall to attach itself to. This creates a major "sticky" clean-up problem. To avoid this problem, a system of chemicals are added to the water "curtain" fluid to "neutralize" the paint to prevent it from sticking to any side wall. This neutralizing process, referred to in the industry as the "detackification" process, chemically alters the paint resin systems so that the paint from this point on cannot be used as a coating. Moreover, the intractable nature of the detackified paint precludes easy recovery of valuable paint compounds such as pigments, solid fillers, and higher boiling point paint solvents. The paint is a cured solid which has to be disposed of. These detackified paint solids floating around in this water curtain or flood sheet fluid (which is in continuous motion) cause foam to be generated. Additional chemicals have to be added to the flood sheet fluid to control this tendency to foam. Since there is some distance between where the paint is sprayed and the point at which the air-borne paint comes in contact with the flood sheet fluid, some of the air-borne paint contacts the walls and the floor of the booth.
The walls and floor, as well as any other paint application equipment in the booth, will build up a thick, tacky coating of this paint if it is not cleaned off on a regular basis. To do this cleaning, various low-boiling solvent systems are utilized. These solvents either end up in the water curtain fluid to be recirculated and eventually evaporate into the air, which is let out to the outside environment, or having low solubility in water, directly pass to the environment.
Current paint applications and clean-up technologies provide no means of trapping the low boiling (highly evaporative) solvents that are used to dilute the paint to a viscosity suitable for spray applications. These solvents also end up evaporating out of the flood sheet fluid system.
Currently, volatile organic solvents are used to flush the unsprayed paint from the spray guns and the bells, and are also used to clean the outside of the hand-operated spray guns in a soak trough. These solvents are in contact with the air in the booth, and approximately forty percent (40%) of the solvent evaporates into the air of the booth. This increases the chances of worker exposure to harmful solvents and also adds these solvents to the air stream which will ultimately be discharged to the outside environment. Additionally, it increases the number of flammable formulations or chemicals that a manufacturer who uses a paint spray booth must have in storage, thus increasing his cost and the chances of accident during their handling.
The proposed invention permits a single formulation to be used for all activities related to paint spray booth clean-up, thus minimizing the chemical hazard safety training required of the paint spray booth operators, the inventory diversity needed to be maintained by the owner, and the quantity of volatile chemicals released to the environment.
An improvement on the current water flood sheet technology to address the problem of trapping some of the paint diluent solvents as well as a portion of the paint booth clean-up solvents is disclosed by the Nalco Chemical Company in their U.S. Pat. No. 4,378,235. This U.S. Patent discloses replacing the water flood sheet fluid with an oil-in-water emulsion system which has been demonstrated to reduce the amount of low boiling solvents evaporating to the open environment. To avoid the cost of re-filling the flood sheet fluid system in the paint booth every time that the paint solids level reached an unmanageable concentration, the oil-in-water emulsion system is continually being reprocessed through a distillation unit. This process is defined in U.S. Pat. No. 4,750,919. Nalco refers to this system as the Hydrocarbon Emissions Controls (HEC) system. The paint trapped by the oil-in water emulsion employed in the HEC system is neutralized or "detackified". This is taught in U.S. Pat. No. 4,750,919. The resultant paint solids cannot be used as a coating. Moreover, the intractable nature of the detackified paint precludes easy recovery of valuable paint compounds such as pigments, solid fillers, and higher boiling point paint solvents. The solids are carried off to be incinerated. The use of low-boiling solvents to clean up the paint overspray on the walls and floor of the paint spray booth is still required with the HEC system.
Accordingly, it would be an advance to the art if a method could be developed for the reclamation of paint and reduction and recovery of volatile organic carriers from paint spray booth systems using an economical absorbing fluid.
A further object of this invention is to provide for the recovery of the paint without detackification, such that said recovered paint could be recycled either in part or as a whole formulated paint.